js:click elsewhere to hide divs

html代码(简化)：

<span id="rule">规则</span>

<div style="display:none" class="wxbgc1" id="hd_rule">
    <p id="hd_rule_p">
      <b>活动规则</b>
    </p>
</div>

js代码:

$(document).bind('click', function(e) {  
    var e = e || window.event; //浏览器兼容性   
    var elem = e.target || e.srcElement;  
    while (elem) { //循环判断至跟节点，防止点击的是div子元素   
        if (elem.id && elem.id == 'hd_rule_p') {  
            return;
        }
        if (elem.id && elem.id == 'rule') {  
            $("#hd_rule").css("display","block");
            return;
        }
        elem = elem.parentNode;  
    }  
    $('#hd_rule').css('display', 'none'); //点击的不是div或其子元素   
});